In high-frequency switching circuits, typical control or signal frequencies are disposed approximately within the microwave range, that is, between 300 MHz (megahertz) and 300 GHz. Such switching circuits are used in different fields, for example, in power amplification, low-noise amplification, for high-frequency switches and so on. Switching circuits can be embodied as integrated circuits, that is, for example, in the form of one or more chips. ICs of this kind can be embodied, for example, as MMICs (“Monolithic Microwave ICs”), in which active and passive components are realised on a single semiconductor substrate.
For the embedding of general integrated circuits or chips in relatively large components, it is already known, for example, that at least one chip can be accommodated in a housing. The resulting component or “package”, that is, the housing with the chip, is then assembled on a printed-circuit board. Many different packaging solutions are known. For example, modern packages frequently no longer have any wire connections, but are provided as SMDs (“surface-mounted devices”) with connecting elements capable of direct soldering, which allow a direct soldering of the package or respectively component onto the printed-circuit board, for example, by means of SMT (“surface-mounting technology”). This is associated with opportunities for automated fitting and mounting on the printed-circuit board, for example, using reflow soldering or re-melting soldering (“reflow soldering”). The extensive automation allows cost-favourable manufacturing methods.
The following can be named as examples of known packaging solutions in the SMD/SMT field: QFN (“Quad Flat No Leads Package”), wherein the electrical connections are integrated flush in a underside of the housing; BGA (“Ball Grid Array”), wherein the terminals are provided in the form of solder beads in a grid on one side of the housing and the beads are connected with contacts on the printed-circuit board, for example, by means of reflow soldering; eWLB (“embedded Wafer Level Ball Grid Array”), wherein the housing terminals are present on a synthetically manufactured wafer made from the chip and a moulding compound; and further developments of the BGA technology such as CSP (“Chip Scale Package”), etc.
Packaging approaches such as those named above are suitable for the embedding of high-frequency chips in relatively large component groups only with some reservations. For example, high-frequency switching circuits can provide considerable thermal-power losses during operation. With the known packaging solutions, an adequate heat removal is not possible without difficulty.
Additionally or alternatively, resonators may be required for high-frequency components or respectively switching circuits, which, in the case of the known packaging solutions, cannot be provided in the required manner and/or in a cost-favourable manner.
Various special packaging solutions are known for the field of high-frequency chips; these generally relate to flange housings. For example, it is known that a cooling element, for example, made from gold-plated copper, can be bonded to a laminate frame which surrounds the chip. Connecting surfaces guided outwards are provided on the laminate. The laminate together with mounted connecting lines and the chip are mechanically protected by a cap. For assembly, a recess must be provided in the printed-circuit board in order to receive the cooling element. The component is assembled by screwing the cooling element into the recess with the printed-circuit board. A heat removal from the chip is achieved via the component's own cooling element, the printed-circuit board and, for example, further cooling elements on the rear side of the printed-circuit board. The electrical contact is made manually by soldering the terminals to corresponding connecting surfaces of the printed-circuit board.
With other methods, the electrical contacting takes place in a manual process by means of bonded, soldered or welded tapes, strips or bonding wires. Alternatively, an appropriately mounted compression element with conductive structure can be used for the contacting by means of corresponding clamping. The compression element is screwed to a stabilising cooling element.
By comparison with the SMD solutions described above, these special approaches for the embedding of high-frequency chips offer an improved thermal connection since the package has at its disposal, for example, its own cooling element for heat removal via the printed-circuit board. However, the lack of SMD capability counteracts this improved heat removal.
DE 10 2010 009 984 A1 describes a printed-circuit board backed with a cooling element. A recess in the printed-circuit board corresponds with an indentation in the cooling element. An amplifier component, which is screwed to the cooling element via screw connections, is arranged in the indentation. An automatic fitting of the printed-circuit board with the component and a reflow soldering are possible, but the component and the cooling element must be screwed together manually.
One object of the present invention is to propose a structure for the embedding of switching circuits which, on the one hand, allows a heat removal which is optimised with regard to the assembly and/or operation, for example, of high-frequency switching circuits, and, on the other hand, which allows automation in the fitting and or the electrical connection to a printed-circuit board.